The invention relates to a laminating station with two heated laminating rollers, between which there is an adjustable nip.
Lamination carriers, such as, for example multi-layers, metal plates, carrier boards for printed circuits and the like, after being cleaned, washed and dried, are supplied to a laminating station or to a film roller mechanism, in which a film is laminated under pressure and heat onto the opposite sides of a carrier.
Preliminary published European Patent Applications No. 0,040,842, No. 0,040,843, and No. 0.041,642 have disclosed laminating devices, in which a substrate or a carrier is laminated on both sides with a dry resist under applied pressure. The dry resist for the particular side of a carrier to be laminated, for example a carrier board for printed circuits, is drawn off from a supply roll and supplied to a pair of liminating rollers, through the nip of which run the two dry-resist films and the carrier located between them. Before lamination, a thin liquid layer is coated onto the surface of the carrier or the carrier board for printed circuits and forms an intermediate layer between the surface of the carrier board and the particular dry-resist film during lamination. This thin liquid layer is removed from the surface of the circuit board, during lamination, by being absorbed into the dry-resist film.
U.S. Pat. No. 4,214,936 relates to a laminating apparatus in which horizontally transported boards, which are moved forward continuously and contact-heated, are laminated on both sides, the peripheral speed of the laminating rollers being greater than the feed speed of the boards. As soon as a sensor detects the rear edge of the preheated board shortly before it enters the nip between the laminating rollers, the latter are stopped only after a certain delay time allowing the rear edge of the board to pass through the laminating nip. When the front edge of the following board is detected, the laminating rollers start to rotate again and the board which has entered the nip is laminated.
European Patent Application No. 0,058,421 makes known a laminating station with two laminating rollers which are both driven from the same motor via sprocket wheels. As soon as a board to be laminated approaches the laminating rollers, the front edge of the board is detected by a sensor, the signal of which sets in motion the drive motor for the laminating rollers. A signal from a second sensor which detects the front edge of the board triggers the closing of the laminating rollers. The laminating rollers close at the moment when the front edge of the board reaches the nip between the rollers. When the rear edge of the board passes a further sensor, a signal which opens the laminating rollers again is generated. The laminating rollers are opened and closed by means of a crank mechanism.
U.S. Pat. No. 4,214,936 describes a laminating station comprising two heated laminating rollers, the upper laminating roller of which is pressed against the fixed lower roller by a pneumatic pressure cylinder. The pressure cylinder exerts an appropriate pressure force of the order to magnitude of approximately 25 N on the two ends of the movable axle of the upper laminating roller. A sensor detects the front edge of a board to be laminated, which is transported towards the laminating station. The sensor signal causes the laminating rollers to rotate. The board and the dry-resist films to be laminated onto both sides of it press open the nip between the laminating rollers, so that these materials can run through.
With known laminating stations, either there is present a nip between the laminating rollers or the laminating rollers are pressed together pneumatically by means of a predetermined pressure force, and are pushed apart to the width of a nip only by the composite structure comprising a board and the films to be laminated onto its, so that the composite structure can be transported through between the laminating rollers. It is obvious that, as regards material thicknesses of the composite structure, which can be, for example, in the range from 0.5 to 7 mm, problems can arise when the laminating rollers are pushed apart. Also, when the material thicknesses vary it is not always expedient to work with a constant laminating pressure for all material thicknesses, such as is exerted in the known laminating stations. When the thickness of the composite structure comprising the board and resist films changes, or different laminating pressures are required for varying material properties, time-consuming conversion work has to be carried out on the known laminating station in order to vary the nip distance between the laminating rollers. This is accomplished through removal and readjustment of at least one of the laminating rollers, through variation of the working pressure of the pneumatic cylinder, or even through exchange of the pneumatic cylinder for another cylinder with a different characteristic. These procedures result in a change in the laminating pressure of the rollers exerted on the composite structure comprising the board and resist films.
In known laminating stations, there is also the problem that one laminating roller is often not mounted exactly parallel to the other laminating roller in every position and at every nip distance. This means that the carriers, such as, for example, circuit boards, experience slight distortion when they run through the nip between the laminating rollers. Relatively long film sheets thus cannot be laminated parallel to the edges of the carrier in the direction of run.